If I post an image or html page with content I regret (say to blogger, jaiku, twitter, wordpress.org), I know I can take down the page and then I may need ask archive.org to remove the page.
Are there other steps I should take to finish scrubbing the internet of accidental postings?
Are there any steps I should take when publishing my content to make it easier to retract?
You'll never be able to ensure that it's not archived/captured somewhere.
Depending on how quickly your content gets crawled by the search engines you probably need to ask them to remove it. (How to get content removed from Google) Even if you do this with the big three search engines there are countless other bots crawling the web that may have captured the content and, even if you could find out what they are, there's no guarantee you'll be able to get them to remove the data.
As for how to prevent such accidental leaks in the future: Utilize whatever tools you have to publish in the future. Even setting to publish 15 minutes into the future still keeps the general immediacy but allows you a few minutes to change your mind.Tweet